RT device recommendations.

I've admired RT for quite a while now, I've loved the way Metro looks, and ever since I got the 928 before summer I've been using a good amount of different Windows services alongside my Google ones (Bing Weather, News, Outlook, Skydrive just to name a few), and the current computer that I have (A Samsung Series 3 Chromebook) doesn't make for the best companion for my phone. So basically I want to put my money where my mouth is and buy an RT device, and take the plunge and fully take advantage of Microsoft's services. So basically, I'd like to ask you Microsoft connoisseurs and experts what RT devices are a good deal.

I know a new Nokia and Microsoft tablet will come out soon, but I would like to see if anything that is out now would still be good or relevant. My only criteria is,

-Must be RT, no Windows 8 tablets.

-Sub $500 (and by under $500 I don't mean $499.99)

-Decent build

-Must be able to be used as tablet (I'm not sure if there are any strictly laptop RT devices, but just in case).

-USB port would be great, but if it doesn't have one it isn't a deal breaker, and while it isn't a necessity, an SD card slot would be perfect.

Thank you for all and any help given.